Exhaust manifold stiffening ribs

ABSTRACT

An exhaust manifold apparatus for routing an exhaust gas produced by an internal combustion engine is described. The manifold includes a manifold log with a log wall that defines a log bore. The log bore is in fluid communication with an upstream opening of the manifold log and a downstream opening of the manifold log. An inlet runner includes a runner wall that defines a runner bore in fluid communication with the log bore. The inlet runner is engaged to the manifold log at a stress point, which also includes at least one stiffening rib disposed on an interior surface of the log wall and/or the inlet runner wall.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/564,379, filed Oct. 4, 2017, which is the U.S. national phase of PCTApplication No. PCT/US2015/025058, filed Apr. 9, 2015, the entiredisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to exhaust manifold assembliesfor use in routing exhaust gases from an engine to an associatedaftertreatment system.

BACKGROUND

Internal combustion engines typically use accompanying exhaust manifoldsto route exhaust gases produced from the combustion process away fromthe engine. Exhaust gas gives off heat as it travels through thedownstream exhaust manifold. As such, while an internal combustionengine is in operation, a cumulative flow of exhaust gas through theexhaust manifold can give off enough heat to raise the temperature ofindividual manifold components, which may cause some components toexpand. Over the course of one or several periods of operation, varyingamounts of exhaust gas traveling through an exhaust manifold can changethe temperature of individual exhaust manifold components several times,thereby causing those components to expand and contract.

SUMMARY OF THE INVENTION

One embodiment relates to a manifold for routing an exhaust gas. Themanifold includes a manifold log, an inlet runner, and at least onestiffening rib. The manifold log includes a log wall having a first logthickness and defining a log bore. The log bore is in fluidcommunication with a first opening at an upstream end of the manifoldlog and a second opening at a downstream end of the manifold log. Theinlet runner is operatively connected to the manifold log at the firstopening, and includes a runner wall having a first runner thickness anddefining a runner bore. The inlet runner includes a third opening at adownstream end thereof in fluid communication with the first opening ofthe manifold log, and a fourth opening at an upstream end thereof. Theinlet runner engages the manifold log at a stress point. At least onestiffening rib is disposed on an interior surface of the log wall and/orthe runner wall and is exposed to a bore at the stress point.

Another embodiment of the invention relates to a manifold assembly forrouting an exhaust gas. The manifold assembly includes a plurality ofinlet runners, a manifold log, and a plurality of stiffening ribs. Theplurality of inlet runners are in fluid receiving communication with acylinder head at upstream ends thereof; and are operatively engaged toand in fluid providing communication with the manifold log at acorresponding plurality of stress points at downstream ends thereof.Each of the plurality of inlet runners includes a runner wall having afirst runner thickness. The manifold log is in fluid receivingcommunication with the plurality of inlet runners at the correspondingplurality of stress points, and is also in fluid providing communicationwith at least one outlet. The manifold log includes a log wall withhaving a first log thickness. Each of the plurality of stiffening ribsare disposed on an interior surface of at least one of the log wall andrunner wall at one of the plurality of stress points. A stiffening riband the log wall in combination provide a second log thickness, and astiffening rib and the runner wall in combination provide a secondrunner thickness, respectively.

Yet another embodiment of the invention relates to a method of formingan exhaust manifold. The method includes forming a manifold log thatincludes a log wall and a log rib. The log wall is formed to have afirst log thickness and define a log bore in fluid communication with afirst opening at an upstream end of the manifold log and a secondopening at a downstream end of the manifold log. The log rib is disposedon an interior surface of the log wall is exposed to the log bore in thevicinity of the first opening. The log rib and the log wall incombination provide a second log thickness. The method further includesforming an inlet runner having a runner wall with a first runnerthickness and defining a runner bore. The inlet runner has a thirdopening at a downstream end thereof and a fourth opening at an upstreamend thereof. The third opening is operatively connected to and in fluidcommunication with the first opening of the manifold log. The methodalso includes coupling the manifold log to the inlet runner at a stresspoint. The stress point is defined by a portion of at least one of thelog wall and the runner wall at a junction where the first opening ofthe manifold log is operatively connected to the third opening of theinlet runner. The stress point is subject to greater amounts of heatfatigue than other portions of the log wall and the runner wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1A is an illustrative diagram of an internal combustion engine,according to an example embodiment.

FIG. 1B is an illustrative diagram of an arrangement of exhaustmanifolds associated with the internal combustion engine shown in FIG.1A.

FIGS. 2A-2C depict three views of an exhaust manifold component of thearrangement shown in FIG. 1B.

FIG. 3A is an illustrative diagram showing an example deformation of theexhaust manifold component shown in FIGS. 2A-2C.

FIG. 3B is an illustrative diagram of a damaged version of the exhaustmanifold component shown in FIGS. 2A-2C, according to an exampleembodiment.

FIGS. 4A-4C depict three views of an exhaust manifold component of thearrangement shown in FIG. 1B that includes a pair of stiffening ribs,according to an example embodiment.

FIG. 5 is a flow diagram showing steps of a method of crafting anexhaust manifold with a stiffening rib, according to an exampleembodiment.

References are made to the accompanying drawings throughout thefollowing detailed description. In the drawings, similar symbolstypically identify similar components, unless context dictatesotherwise. The illustrative implementations described in the detaileddescription, drawings, and claims are not meant to be limiting. Otherimplementations may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presented here.It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thefigures, can be arranged, substituted, combined, and designed in a widevariety of different configurations, all of which are explicitlycontemplated and made part of this disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1A, an internal combustion engine 100 is configured tocyclically collect and ignite fuel from an associated fuel system andair from the intake system to generate a mechanical force. In variousarrangements, the internal combustion engine 100 is configured toconsume fuel in the form of gasoline (including variants thereof such asmixtures of gasoline and ethanol, E-85, and the like), diesel (includingvariants thereof, such as biodiesel), natural gas, or other similarlycombustible fuels. As a result of each cycle of collection and ignition,an exhaust gas is created. In various arrangements, the internalcombustion engine 100 includes a plurality of cylindrical bores withinwhich the collection and ignition process takes place. In sucharrangements, an associated cylinder head with intake and exhaust portsregulates the flow of intake gas into each cylinder and the flow ofexhaust gas out of each cylinder, respectively. As such, a manifoldassembly 101 in fluid communication with the cylinders (e.g., engaged tothe cylinder head) can be configured to collect exhaust gas from thecylinder head of the internal combustion engine 100 and route theexhaust gas to an aftertreatment system. As will be appreciated from thediscussion that follows, heat accumulating from a flow of exhaust gasthrough the manifold assembly 101 can cause individual component partsto expand and contract, which can ultimately cause some of thosecomponent parts to fail as a result of heat fatigue.

Referring to FIG. 1B, the manifold assembly 101 is an examplearrangement of a plurality of removably engaged manifold components thatcan include a single head manifold portion 102, a double head manifoldportion 104, a bellows 106, an inlet 108, and an outlet 110.Specifically, in the embodiment shown in FIG. 1B, the manifold assembly101 includes two exhaust gas flow circuits that are overall in parallel,each circuit including three double head manifold portions 104 in a rowwith a single head manifold portion 102 at either end of each row (i.e.,a total of two single head manifolds 102 for each circuit), eachmanifold component being interconnected via a bellows 106 (i.e., for atotal of four segments of bellows 106 in each circuit).

The single head manifold portion 102 and the double head manifoldportion 104 define interconnected conduits, each of which beingconfigured to engage the cylinder head at an upstream end of themanifold assembly 101 and route an incoming flow of exhaust gas to theoutlet 110 at a downstream end of the manifold assembly 101. Eachmanifold includes at least one inlet 108 (i.e., the single head manifoldportion 102 includes one inlet 108, and the double head manifold portion104 includes two inlets 108), each of which being in fluid receivingcommunication with at least one exhaust port disposed in the cylinderhead. In this particular arrangement, the manifolds are interconnectedby a bellows 106 at each inter-manifold junction. The bellows 106 is aflexible conduit configured to allow for a range of deformation whileaccommodating a gas flow through a hollow bore within. In operation, anexhaust gas flow from the cylinder head originates from at least oneinlet 108, flowing downstream through at least one manifold (e.g., asingle head manifold portion 102 or a double head manifold portion 104),and out through at least one outlet 110 into the remainder of anassociated exhaust system.

Although FIG. 1B shows one particular example arrangement of themanifold assembly 101, various configurations of the manifold assembly101 can be fashioned to fit a variety of applications. In somearrangements, an individual manifold component or portion can have morethan one or two heads (e.g., a triple head or quadruple head manifoldportion with three or four inlet runners, respectively). Further,individual manifold components or portions can be interconnected withother manifolds or conduits in the absence of a bellows 106 (e.g., adouble head manifold portion 104 can be directly engaged to a singlehead manifold portion 102). In addition, a given manifold assembly 101can be configured such that some manifold components or portions includeone or more outlets 110, while other components do not include anyoutlets 110 (e.g., one double head manifold portion 104 in a circuitcontains an outlet 110 while an adjacent interconnected double headmanifold portion 104 does not; or a double head manifold portion 104includes two outlets 110, while adjacent interconnected manifoldportions have no outlets 110). In some arrangements, the manifoldassembly 101 only has one manifold component (e.g., one double headmanifold portion 104 with an outlet 110, and no interconnected manifoldsor bellows).

Referring to FIG. 2A, a first double head manifold 200 includes a log202, a first connector 204, a second connector 206, a first inlet 208, asecond inlet 214, and a manifold outlet 220. The log 202 is a conduitwith a hollow bore in fluid communication with a first openingcorresponding to the first connector 204 at one end, and a secondopening corresponding to the second connector 206 at the opposite end.The first connector 204 and second connector 206 each define aninter-manifold junction, wherein another manifold component or portioncan engage and be in fluid communication with the first double headmanifold 200. In some arrangements, the first connector 204 and secondconnector 206 can be configured to engage a bellows (e.g., bellows 106)disposed at an inter-manifold junction.

The first inlet 208 and the second inlet 214 are each in fluid receivingcommunication with at least one exhaust port of a cylinder head, anddefines a third and fourth opening in the double head manifold 200,respectively. In addition, a first flange 212 and a second flange 218are annularly disposed about the first inlet 208 and second inlet 214,respectively. The first flange 212 and the second flange 218 areconfigured to provide strong points of engagement between the firstdouble head manifold 200 and a corresponding cylinder head. In somearrangements, both flanges 212, 218 include a plurality of boresconfigured to accommodate a corresponding plurality of bolts. As such,bolts disposed through the flange bores and into the cylinder head canbe used to secure the flanges 212, 218, and therefore the first doublehead manifold 200, to the cylinder head.

A first inlet runner 210 and a second inlet runner 216 are configured toroute an exhaust gas flow received from a cylinder head at the firstinlet 208 and the second inlet 214, respectively, to the log 202. Thefirst inlet runner 210 is a conduit in fluid communication with the log202 at a downstream end and the first inlet 208 at an upstream end. Thesecond inlet runner 216 is also in fluid communication with the log 202at a downstream end, and the second inlet 214 at an upstream end. Thefirst inlet runner 210 and the second inlet runner 216 extend laterallyfrom the log 202 (e.g., approximately perpendicular to the log 202), andare configured to allow the first inlet 208 and the second inlet 214 toengage a cylinder head. As can be appreciated in FIG. 2A, the firstinlet runner 210 and the second inlet runner 216 are disposedapproximately in parallel relative to each other.

Referring to FIG. 2B, in this particular embodiment, the wall thicknessof the log 202 forming the interior bore is substantially uniform. Inaddition, referring to FIG. 2C, the inner wall of the log 202 betweenthe first inlet runner 210 and the second inlet runner 216 issubstantially smooth and uniform as well.

Referring to FIG. 3A, in operation, an exhaust gas flow from a cylinderhead 302 through the first double head manifold 200 begins at the firstinlet 210 and the second inlet 214. The gas flow subsequently travelsinto the log 202 and out the manifold outlet 220. Additional gas flowsfrom adjacent manifolds (e.g., other single or double head manifolds,which may be engaged to the first double head manifold 200 via abellows) can also travel downstream into the first connector 204 and thesecond connector 206, into the log 202, and out the manifold outlet 220.Exhaust gas from a plurality of inlet runners (i.e., first inlet runner210, second inlet runner 216, and inlet runners associated with adjacentmanifold components or portions that are engaged to the first doublehead manifold 200) and a corresponding plurality of exhaust portstherefore collect and flow through the log 202 before flowing out of themanifold outlet 220. In operation, as one skilled in the relevant artwould recognize, the configuration of the inlet runners 210, 216 asengaged to the manifold log 202 causes stress at distinct areas of thedouble head manifold 200 in the manner discussed below. These areaswhere stresses occur are referred to herein as “stress points.”

In this particular embodiment, the first flange 212 and the secondflange 218 securely fasten the upstream end of the first inlet runner210 and the second inlet runner 216 to the cylinder head 302, limitingthe ability of the log 202 to expand. During operation, the log 202weakens and tends to expand to a greater degree than the cylinder head302. Both the first inlet runner 210 and the second inlet runner 216extend from a common side of the log 202 and are securely fastened tothe cylinder head 302, preventing adjacent portions of the common sideof the log 202 to slide as the log 202 seeks to expand. As a result, acompression effect occurs and the log 202 yields and compresses at astress point 303 located at the medial side of each inlet runner-logjunction. The first inlet runner 210 and the second inlet runner 216 arethus disposed at an irregular angle relative to each other due to thecompression at each stress point 303, as opposed to being disposedapproximately in parallel as discussed above with respect to FIG. 2A.Over the course of an internal combustion engine's lifetime, suchcompressions can occur many times and to various degrees based on numberof uses (i.e., the number of periods of operation) or engine load (e.g.,periods of heavy load and periods of light load).

Referring to FIG. 3B, fatigue caused by compressions and deformations asdiscussed with respect to FIG. 3A over the life of a given internalcombustion engine can cause an exhaust manifold to fail. In onearrangement, heat fatigue gives rise to a first failure 304 and a secondfailure 306. The first failure 304 is a crack in the log 202 at thestress point 303 adjacent to the first inlet runner 210. Accordingly,the second failure 306 is a crack in the log 202 at the stress point 303adjacent to the second inlet runner 216. The first failure 304 and thesecond failure 306 can result in a number of functional issues in theassociated internal combustion engine. For example, where the internalcombustion engine includes a turbocharger, the first failure 304 and thesecond failure 306 can result in a decreased flow of exhaust gas to theturbocharger (i.e., where some exhaust gas escapes from cracks at thefirst failure 304 and/or the second failure 306), thereby hindering theperformance of the turbocharger. As another example, where an associatedexhaust assembly disposed downstream from the first double head exhaustmanifold 200 includes one or more sensors (e.g., an O2 sensor exposed toa flow of exhaust gas in the exhaust assembly), a leak at the firstfailure 304 and/or the second failure 306 can result in additionalissues stemming from inaccurate sensor readings (e.g., the internalcombustion assembly running rich or lean as a result of inaccurate O2readings).

As yet another example, the first flange 212 and the second flange 218can ratchet closer to each other over time as a result of cyclic thermalcompression and yielding, ultimately causing associated flange fasteners(e.g., threaded bolts or screws) to fail (e.g., where the ratchetingaction causes flange bolts to shear). In addition, the ratcheting actioncan cause the first flange 212 and/or the second flange 218 to becomemisaligned with the cylinder head 302, preventing the first double headmanifold 200 from being remounted to the cylinder head 302 (e.g., duringan engine rebuild or some other service event). Further, with respect toother aspects of an associated manifold assembly (e.g., the manifoldassembly 101), as the first flange 212 and the second flange 218 ratchetcloser together over time, the overall size of the log 202 can shrink,thereby impeding the ability of the first double head manifold 200 toengage other manifold components. For example, where the first doublehead manifold 200 is engaged to another manifold component by a bellows(e.g., bellows 106), the log 202 may shrink to such an extent that thebellows is unable to connect the first double head manifold 200 toanother manifold component. As a result, the bellows and/or the firstdouble head manifold 200 may need to be replaced during a service eventbefore the associated manifold assembly can be reassembled.

Referring to FIG. 4A, a second double head manifold 400 includesadditional features configured to inhibit heat fatigue-based failure atthe stress points 303. The second double head manifold 400 is configuredto fit the same applications as the first double head manifold 200, andas can be appreciated from FIG. 4A, the second double head manifold 400also maintains a substantially similar size, shape, and outwardappearance as the first double head manifold 200.

Referring to FIG. 4B, the second double head manifold 400 includes afirst log rib 402. The first log rib 402 is a section of the log 202wall with an increased log wall thickness relative to other sections ofthe log 202. In particular, the first log rib 402 protrudes into the log202, effectively narrowing a portion of the bore defined by the log 202that includes the first log rib 402. In some arrangements, the increasedwall thickness associated with the first log rib 402 can extend into thefirst inlet runner 210, such that a portion of the first inlet runner210 wall is thickened as well, which is discussed in more detail withrespect to FIG. 4C, below.

Referring to FIG. 4C, as mentioned above with respect to FIG. 4B,stiffening ribs are disposed in the second double head manifold toprovide support at the stress points 303. Stiffening ribs are supportingsegments of additional material (i.e., material used to form a givenmanifold, such as iron, steel, alloys, and the like) substantiallydisposed on a bore-facing segment of a given manifold. In the doublehead manifold arrangement shown, the first log rib 402 and a second logrib 404 are disposed in the log 202, each of which protrude into thebore of the log 202. In addition, a first runner rib 406 and a secondrunner rib 408 are disposed in the first inlet runner 210 and secondinlet runner 216, respectively. In arrangements such as the seconddouble head manifold 400 shown, a log rib (e.g., first log rib 402) canbe formed such that it continues into an adjacent runner rib (e.g.,first runner rib 406). The stiffening ribs are disposed in the seconddouble head manifold 400 along the medial surface of the two inlet-logjunctions in the vicinity of the stress points 303.

Referring to FIG. 5, a method 500 of forming an exhaust gas manifoldincludes forming a manifold log (e.g., log 202) at 502. The manifold logis formed through any of several manufacturing processes including, forexample, casting, stamping and rolling, and so on. The manifold log canalso be made up of any of several materials including iron, steel,aluminum, and so on, including alloys thereof. The manifold log isformed as a conduit with at least two openings, one opening disposed atan upstream end of the manifold log and another opening disposed at adownstream end of the manifold log, with both openings being in fluidcommunication with a log bore running through the length of the manifoldlog. The log bore is defined by a log wall with a first log thicknessthat gives rise to the overall shape of the manifold log and the crosssectional area of the log bore. In some arrangements, the first logthickness is generally consistent throughout the manifold log, with theexception of additional features to fit specific applications (e.g.,flanges, bolt holes, clamp seats, and so on).

In some arrangements, a stiffening rib (e.g., first log rib 402) isformed along with the manifold log at 502. The stiffening rib is a logwall portion with an increased wall thickness relative to other portionsof the log wall. In some arrangements, the manifold log can be formedwith a stiffening rib disposed on the log wall such that the stiffeningrib effectively narrows the log bore. The stiffening rib can be formedsimultaneously during the forming of the manifold log at 502, or can beadded after the initial forming of the manifold log at 502. For example,in one embodiment, the stiffening rib can be included in the log wall asthe manifold log is casted. In another embodiment, the stiffening ribcan be welded into a preexisting log wall and runner wall.

At 504, at least one inlet runner (e.g., inlet runner 210) is formed.The inlet runner can be formed via the same or similar types ofmanufacturing processes as the manifold log, and can be made up of thesame or similar types of materials. The inlet runner can also be formedas a conduit with at least two openings, one at an upstream end andanother at a downstream end, both of which being in fluid communicationwith a runner bore disposed through the length of the inlet runner. Therunner bore is defined by a corresponding runner wall with a firstrunner thickness giving rise to the overall shape of the inlet runnerand the cross sectional area of the runner bore. In some arrangements,the upstream end of the inlet runner is configured to removably engage aportion of a cylinder head that includes at least one exhaust port(e.g., where the upstream end of the inlet runner includes a flange).The downstream end of the inlet runner is configured to engage theupstream end of the manifold log, such that the downstream opening ofthe inlet runner is in fluid communication with the upstream opening ofthe manifold log. In some arrangements, the inlet runner is formedseparately and is later coupled to the manifold log. In otherarrangements, the inlet runner is formed together with the manifold log,and as such, the inlet runner and manifold log are formed as asingle-piece, monolithic unit.

Also similar to the forming of the manifold log at 502, the inlet runnercan be formed at 504 to include a stiffening rib (e.g., first runner rib406) as well. The stiffening rib here can be a runner wall portion withan increased wall thickness relative to other portions of the runnerwall. The stiffening rib in the inlet runner formed in the inlet runnercan be made in a similar way as the stiffening rib formed in themanifold log at 502 (e.g., narrowing the runner bore, integrally formedwith the inlet runner or separately and later added, and so on). In somearrangements, the stiffening rib is a single, continuous rib that beginsat a runner rib and continues to and extends through a log rib. Further,the stiffening rib can also be a single, continuous rib that begins at afirst runner rib, continues to and extends through a log rib, andcontinues to and terminates at a second runner rib.

At 506, a stress point (e.g., stress point 303) is formed. The stresspoint typically is formed in the vicinity of the junction where themanifold log joins the inlet runner. The stress point is an area of thelog wall and/or the runner wall that is subject to heat fatigue due toan unequal deformation of the inlet runner with respect to the manifoldlog, as a result of a distribution of heat arising from a flow ofexhaust gas within the runner bore and the log bore. Further, the stresspoint can be formed such that it includes a log rib and/or a runner rib.In some arrangements, the inlet runner and the manifold log togetherdefine two angles at the inlet runner-manifold log junction: a largeangle and corresponding a small angle. The small angle is a resultingangle that is less than 180 degrees, and the corresponding large angleis a resulting angle that is greater than 180 degrees (i.e., the smallangle and the large angle together add up to 360 degrees). For example,in an embodiment where the manifold log and the inlet runner gives riseto an overall perpendicular shape, the small angle is 90 degrees and thecorresponding large angle is 270 degrees. In such an example, the stresspoint can include areas of the log wall and the runner wall that definesthe small angle.

As utilized herein, the terms “substantially” and similar terms areintended to have a broad meaning in harmony with the common and acceptedusage by those of ordinary skill in the art to which the subject matterof this disclosure pertains. It should be understood by those of skillin the art who review this disclosure that these terms are intended toallow a description of certain features described without restrictingthe scope of these features to the precise numerical ranges provided.Accordingly, these terms should be interpreted as indicating thatinsubstantial or inconsequential modifications or alterations of thesubject matter described and are considered to be within the scope ofthe disclosure.

Further, as utilized herein, the term “fluid” is intended to have abroad meaning in harmony with the common and accepted usage by those ofordinary skill in the art to which the subject matter of this disclosurepertains. In particular, it should be understood by those of skill inthe art who review this disclosure that “fluid” contemplates mattercapable exhibiting a flow, and may include matter in a gaseous state, aliquid state, or some combination of components in various states ofmatter.

It should be noted that the orientation of various elements may differaccording to other exemplary embodiments, and that such variations areintended to be encompassed by the present disclosure. It is recognizedthat features of the disclosed embodiments can be incorporated intoother disclosed embodiments.

It is important to note that the constructions and arrangements ofapparatuses or the components thereof as shown in the various exemplaryembodiments are illustrative only. Although only a few embodiments havebeen described in detail in this disclosure, those skilled in the artwho review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter disclosed. For example,elements shown as integrally formed may be constructed of multiple partsor elements, the position of elements may be reversed or otherwisevaried, and the nature or number of discrete elements or positions maybe altered or varied. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes and omissionsmay also be made in the design, operating conditions and arrangement ofthe various exemplary embodiments without departing from the scope ofthe present disclosure.

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other mechanisms and/or structures for performing thefunction and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the inventiveembodiments described herein. More generally, those skilled in the artwill readily appreciate that, unless otherwise noted, any parameters,dimensions, materials, and configurations described herein are meant tobe exemplary and that the actual parameters, dimensions, materials,and/or configurations will depend upon the specific application orapplications for which the inventive teachings is/are used. Thoseskilled in the art will recognize, or be able to ascertain using no morethan routine experimentation, many equivalents to the specific inventiveembodiments described herein. It is therefore to be understood that theforegoing embodiments are presented by way of example only and that,within the scope of the appended claims and equivalents thereto,inventive embodiments may be practiced otherwise than as specificallydescribed and claimed. Inventive embodiments of the present disclosureare directed to each individual feature, system, article, material, kit,and/or method described herein. In addition, any combination of two ormore such features, systems, articles, materials, kits, and/or methods,if such features, systems, articles, materials, kits, and/or methods arenot mutually inconsistent, is included within the inventive scope of thepresent disclosure.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The claims should not be read as limited to the described order orelements unless stated to that effect. It should be understood thatvarious changes in form and detail may be made by one of ordinary skillin the art without departing from the spirit and scope of the appendedclaims. All embodiments that come within the spirit and scope of thefollowing claims and equivalents thereto are claimed.

What is claimed is:
 1. A method of forming an exhaust manifoldcomprising: forming a manifold log including a log wall and a log rib,the log wall having a first log thickness and defining a log bore influid communication with a first opening at an upstream end thereof anda second opening at a downstream end thereof, and the log rib beingdisposed on an interior surface of the log wall and exposed to the logbore in the vicinity of the first opening, wherein the log rib and thelog wall in combination provide a second log thickness; forming an inletrunner including a runner wall having a first runner thickness anddefining a runner bore in fluid communication with a third opening at adownstream end of the inlet runner and a fourth opening at an upstreamend of the inlet runner, wherein the third opening is operativelyconnected to and in fluid communication with the first opening; andcoupling the manifold log to the inlet runner at a stress point, thestress point being defined by a portion of at least one of the log walland the runner wall at a junction where the first opening of themanifold log is operatively connected to the third opening of the inletrunner, wherein the stress point is subject to greater amounts of heatfatigue than other portions of the log wall and the runner wall.
 2. Themethod of claim 1, wherein the manifold log is integrally formed withthe inlet runner as a single-piece construction.
 3. The method of claim1, wherein the manifold log is formed as a separate component that iscoupled to the inlet runner.
 4. The method of claim 1, wherein the logrib is integrally formed with the manifold log as a single-piececonstruction.
 5. The method of claim 1, wherein the log rib is formed asa separate component that is coupled to the manifold log.
 6. The methodof claim 1, wherein the inlet runner is formed to further include arunner rib disposed on an interior surface of the runner wall andexposed to the runner bore in the vicinity of the third opening, whereinthe runner rib and the runner wall in combination provide a secondrunner thickness.